Hydraulic drive cylinder



April 9, 1968 E. F. ALLEN 3,376,795

HYDRAULIC DRIVE CYLINDER Filed Oct. 21, 1965 3 Sheets-Sheet 1 INVENTOR.544946 f. ALLEN April 9, 1968 E. F. ALLEN HYDRAULI C DRI VE CYLINDER 3Sheets-Sheet 2 Filed Oct. 21,, 1965 INVENTOR. 6 4946 f. flue/v 77WT'IMMJAn-awa April 9, 1968 E. F. ALLEN HYDRAULIC DRIVE CYLINDER 3 Sheets-Sheet5 Filed Oct. 21, 1965 United States Patent Ofiice 3,376,795 HYDRAULICDRIVE (IYLINDER Earle F. Ailen, Norwell, Mass, assignor of one-half toValentine E. Macy, In, New York, N.Y. Filed Oct. 21, 1965, Ser. No.499,723 Claims. (Cl. 92-130) ABSTRACT OF THE DISCLOSURE A hydraulicdrive cylinder incorporating a hydraulic motor and having concentricallyarranged spring means which acts coaxially with the hydraulic force andstores energy which is used as a counter-balance to the load being movedby the cylinder. The spring means is connected to the oppositelytelescoped ends of the cylinder and consists of steel or elastomer or acombination of both. The spring means may also be incorporated inindividual hydraulically sealed telescoping cylinders which communicatewith their own source of hydraulic fluid. Solid elastomer cylinders withsteel springs embedded therein as well as laminated elastomers are alsodisclosed for use in this device.

The present invention relates to an improvement in hydraulic drivedevices and more particularly to an improved hydraulic drive meanswherein the drive unit includes an integral energy storage orcounterbalancing means. Hydraulic drive cylinders are widely used forpower sources and particularly for manipulating relatively heavystructures or loads. In many such applications the power required of thehydraulic drive cylinders is reduced by the addition of counterweightsor spring devices on the load which partially offset the gravity forcesresulting from the unbalanced nature of driven structures. One exampleof such a structure is a lift bridge of the bascule type wherein arelatively long bridge span is pivotally mounted at one end for movementbetween a generally horizontal load supporting position and a raisedopen position. The power units used to handle such bridges at presentare conventionally counterbalanced by massive weights to reduce thepower required by the span driving units. Other structures such asderrick or crane booms or heavy tools on construction equipment and thelike also are designed with large weights to counterbalance the normallyunbalanced movably operated elements.

Where such structures are powered by hydraulic cylinders it has beenproposed that these counterweights be eliminated and replaced by storagemeans such as coil springs mounted in or adjacent to the hydrauliccylinders for providing the necessary counterbalancing force. The powerunit of the present invention provides an improved hydraulic drive ofthis type wherein the novel arrangement of the energy storage membersprovides an improved combined hydraulic drive cylinder andcounterbalancing unit incorporated in an integral structure of minimumsize and conveniently adapted for handling very heavy counterbalancingforces without an appreciable increase in the overall size of the powerunit itself. These results have been obtained as will be described belowby a unique arrangement of the counterbalancing eleents and materialsand in one embodiment by the use of elastomers or a combination ofmetallic spring elements with a cooperating elastomer.

Accordingly an object of the present invention is to provide an improvedhydraulic drive cylinder.

Another object of the present invention is to provide an improvedhydraulic drive incorporating an integral counterbalance or energystorage device.

Another object of the present invention is to provide an improvedcounterbalancing means incorporating metallie and elastomeric energystorage.

3,376,? Patented Apr. 9, 1968 Other and further objects of the inventionwill be obvious upon an understanding of the illustrative embodimentabout to be described or will be indicated in the appended claims, andvarious advantages not referred to herein will occur to one skilled inthe art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes ofillustration and description and is shown in the accompanying drawings,forming a part of the specification, wherein:

FIG. 1 is a side elevational view of hydraulic units in accordance withthe present invention applied in the operation of a lift bridge;

FIG. 2 is a vertical sectional view of a preferred embodiment of thehydraulic drive cylinder incorporating counterbalance spring members;

FIG. 3 is a vertical sectional view of the cylinde of FIG. 2 taken alongline 3-3 on FIG. 2;

FIG. 4 is a vertical sectional view corresponding to FIG. 2 showing thecylinder in its extended position;

FIG. 5 is a side elevational view of drive cylinders according to thepresent invention applied to a bridge span;

FIG. 5a is a vertical sectional view taken on line Sa-Sa on FIG. 5;

FIG. 6 is a side elevational view of another embodiment of a bridgedrive in accordance with the present invention;

FIG. 7 is a vertical sectional view of another embodiment of a drivecylinder in accordance with the present invention;

FIG. 8 is a vertical sectional view of the drive cylinder of FIG. 7taken along line 8-8 on FIG. 7;

FIG. 9 is a vertical sectional view of another embodiment of a drivecylinder in accordance with the present invention;

FIG. 10 is a vertical sectional view of the drive cylinder of FIG. 9taken along line 10-10 on FIG. 9;

FIG. II is a vertical sectional view of another embodiment of a drivecylinder in accordance with the present invention;

FIG. 12 is a vertical sectional view of the drive cylin der of FIG. 11taken along line 12-12 on FIG. 11;

FIG. 13 is a vertical sectional view of another embodiment of a drivecylinder in accordance with the present invention;

FIG. 14 is a vertical sectional view of the drive cylinder of FIG. 13taken along line 14-14 on FIG. 13;

FIG. 15 is a vertical sectional view of an additional embodiment of thedrive cylinder in accordance with the present invention; and

FIG. 16 is a vertical sectional view of a still further embodiment ofthe drive cylinder in accordance with the present invention.

FIG. 1 shows a bridge span 1 pivotally mounted at 2 on a solid abutment3. The span 1 as illustrated is driven by a toggle-like combination ofhydraulic drive cylinders or power units 4 and 5 coupled to a commonpivot point 6 and having each of their ends attached to the abutment 3or span 1 as illustrated. The two main drive cylinders 4 are illustratedin their extended position when the span is at its lower position. Asthe span is moved to this position and as will be more fully describedbelow a substantial portion of the span weight or moment iscounterbalanced by an integral energy storing element spacedconcentrically of the cylinders 4 and providing a substantial portion ofthe force required to raise the span 1 to its open position as indicatedin the dash-dot lines.

FIGS. 2 through 4 illustrate a drive cylinder or power unit 4incorporating such an energy storing means in the form of a plurality ofcoil springs 7 concentrically mounted about the tubular casing 8 of thehydraulic Q cylinder 9 and attached to opposite ends 10 and 11 of thepower unit housing and so that the springs 7 are under tension when theunit 4 is in its extended position and when the bridge span 1 is loweredto the position illustrated in solid lines in FIG. 1.

The hydraulic drive 4 including the springs 7 is hereinafter referred toas a power unit. It has a center piston rod 12 and piston 13 slidablymounted in a cooperating and sealed inner cylinder 9 providing thehydraulic drive portion of the power unit 4. Suitable ports 14 areprovided for introducing the hydraulic liquid under pressure to theopposite sides of the piston 13. A housing is provided for thecounterbalancing springs 7 which comprise 14 springs in the preferredembodiment equally spaced concentrically of the power unit cylinder 9,between spaced and slidably engaged telescoping inner and outercylinders 8 and 15. A suitable connecting means 16 is provided on theend plate 10 and the end plate 11 fixedly mounts the piston rod 12 whichhas a convenient coupling 17 provided at its outer end. A fail safehydraulic brake as described in my United States Patent No. 3,203,513 isillustrated at 18 to lock the piston at any position.

The above described concentric mounting including the telescopingcylinders permits the use of a plurality of smaller springs to be usedin a suitable arrangement to provide the necessary counterbalancingforce. This use of a number of small springs provides an important andlarge factor of safety over where the single spring is used and inaddition permits a much larger spring force to be used with improveddeflection characteristics as 1 will be made clear in the followingdiscussion of a typical design for such power units.

The following description provides an illustration of the relativelygreat advantages which are obtained by the use of power units inaccordance with the invention as applied to the spans of a lift bridgeopened and closed by these units. FIG. 1 illustrates a two-span liftbridge spanning a 120 foot channel with each of the spans comprising a60 by 80 foot leaf formed of conventional designs for such spans andpreferably of aluminum so that the individual spans themselves weighabout 168,000 pounds each. Such a leaf under presently used and typicalbridge designs would require a counterweight on the inner end of eachspan to balance the weight of the span. Such a counterweight whosecenter of gravity is necessarily closer to the span pivot than is thecenter of gravity of the span itself must be considerably heavier thanthe span and for a bridge as described would typically consist of aweight of about 600,000 pounds thus adding appreciably to the size andcost of the bridge foundations and the pivots 2.

A drive system will now be described for opening and closing the abovedescribed spans in which this extremely heavy counterweight is replacedby a steel spring counterpoise weighing only about 50,000 pounds orelastomer A springs or combination steel and elastomer springs Weighingonly a fraction of the weight of the steel springs.

For the above span, the initial raising is performed by the jackingdrive cylinders which may be a conventional hydraulic drive cylinder. Toraise the bridge spans from their relatively level position to aninclined position of about 6.5 where the main power units 4 take overthe lifting operation, it has been caculated that a pulling force at thebridge connection of about 100,000# is required which requires a driveforce from the jacking cylinders 5 of about 44,000#. A counterbalancingforce of about 100,000# is now required in power units 4 on each side ofthe span. In the power units 4 employing fourteen springs of the typeillustrated in FIGS. 2 through 4, a spring force in these extendedsprings of about 7,200# per spring is required. The followingcaculations show how this requirement may be conveniently met withrelatively small springs having an outer diameter of 5 in. and formed of1 in. diameter spring steel and with each of the springs deflectingabout 12 ft. from a relaxed 4 length of about 18 ft. to an extendedlength of 30 ft. when the drive cylinders are in the position shown insolid lines in FIG. 1. This is shown by the following typicalcalculation for a spring of these dimensions:

The following calculations indicates the spring size for providing acounterbalancing spring force of about 100,000# with fourteen springs 7surrounding the power cylinder 9. This requires a force of about 7,200#from each of the springs 7.

D is the spring coil size and d is the spring wire diameter.

K is a constant for coiled steel. Assume D/d=5 (stress for springsteel), 7: 120,000 p.s.i. (acceptable d=1").

For D/d=5, K==1.3

r Q L l 8DK 8 5 1.3 -7260d Use P:720Od For 1" wire P=7200 lbs/spring.

Stroke of power units (6)=12. G=constant for coil spring steel.

For a deflection of 12', n=1.6 144=230 coils. Closed length of spring=230 1/l2=19'.

Since the above described counterweight springs essentially balance thespan weights in the beginning of the lifting operation, the maximumhydraulic force required from the power units is determined by thehighest wind pressure forces which must be controlled when the bridge isat its fully raised position of at about as illustrated. Assuming a windforce of 5# per sq. ft. upon the span of this illustration which has anarea of 4,800 sq. ft. the total wind force will be 72,000#. This resultsin a force on the drive cylinders 4, taking the moment arm lengths intoconsideration for this bridge position, of 48,000# with an additional7,500# required to balance the bridge weight at this condition. Thepower units thus require a drive force of 55,000# which is easilyobtained in units having centrally positioned piston with a diameter ofabout 12 in.

It is therefore seen that a pair of spans providing a ft. overall bridgelength are readily controlled by a spring balanced hydraulic drivesystem including relatively small hydraulic drive cylinders each beingonly about 3 ft. in diameter and having a length of only about 18 ft.These units replace counterweights weighing as much as 30 tons or moreand conventional electromechanical drive systems of great complexity andwith correspondly lower dependability.

FIGS. 5 and 5a illustrate a power unit 20 of the general type describedabove where the counterbalancing units are in their position of maximumforce with the drive cylinder closed and with the spring unitscompressed. The driven element 21 representing a bridge span or otherlarge pivotally mounted beam or channel is raised and lowered by a drivesystem including a main drive cylinder 22 and a smaller moving cylinder23 which are pivotally connected at their adjacent ends to a pair ofwide track load supporting wheels 24. As the cross-sectional FIGURE 5ashows, the main drive includes a hydraulic piston 25 which is extendedupon application of the hydraulic force to drive the wheels 24 forwardand to swing the member 21 from its lower position as indicated in solidlines to its raised position as indicated at dash-dot lines. The smallerdrive cylinder 23 is also extended during the raising action tocompensate for the upward swing of the coupling point 26 during thisaction.

The main power unit 22 includes a centrally located hydraulic cylinderpiston 25 and piston rod 28 as shown in sectional FIG. 5a mountedconcentrically with an inner cylindrical brake surface 29 adapted forengagement with an expanding brake shoe mounted on the piston rod and ofthe general type illustrated in my United States Patent No. 3,203,513.The outer portion of the main drive power unit 22 comprises telescopingcylindrical cover portions 30 spaced from the brake surface 29 formingan annular cavity in which a plurality of the counterbalancing springunits 31 are positioned. Each spring 31 itself has a pair of telescopingcylindrical guides 32 which extend to per mit the expansion of thesprings as the springs lengthen towards their normal unstressedcondition.

This construction is thus seen to provide the same advantages discussedabove for the power unit of FIGS. 2 through 4 in a drive cylinder wherethe counterbalancing spring force is provided by a plurality ofindividual units spaced concentrical'y with and positioned about acentral hydraulic drive cylinder and where the springs replace the heavycounterweight and also reduce the drive requirements for the hydrauliccylinders.

FIG. 6 illustrates another bridge structure 34 utilizing a power unit 35in accordance with the present invention and of the general typedescribed above in connection with FIG. 5 where the counterbalancingsprings are compressed when the bridge is in its lowered stage and wherethe weight of the bridge is counterbalanced by this spring compression.This bridge 34 is of the roller bascule type and is particularly suitedfor the application of a spring loaded drive device in accordance withthe present invention. The springs replace all or a substantial portionof the counterweight so that the roller 36 and track 37 are convenientlypositioned in a relatively compact form without the necessity ofadditional track structure or other support weight to accommodate boththe structure of and the substantially increased weight necessary for aconventional counterweighted span.

It has been found that the individual spring units for counterbalancingpurposes of the type described herein may be combined with an elastomersuch as natural or synthetic rubber to provide spring units where therubber substantially increases the spring force available incounterbalancing elements of extremely small size. It has been found,for example, that unexpectedly high counterbalancing forces in theneighborhood of 600 p.s.i. to 4000 psi. with a possible usable maximumof 8000 p.s.i. with 160% elongation may be obtained and retained formany years of operation even under conditions of constant stress.

For example, in a power unit such as described above and illustrated inFIGS. 2 through 4, the 5" diameter springs used in the numerical examplemay be replaced by a series of 5" diameter rubber elements similarlypositioned and anchored at opposite ends of the drive and which provide10,000# per rubber unit as contrasted with the 7,200# counterbalancingforce by the spring described above. It is thus clear that the elastomerunits of this type may be designed for providing similar driving forcesand having a decreased outer diameter.

In addition it has also been discovered that a particularly usefulcounterbalancing unit may be formed from combined spring steel andelastomer units to obtain an extremely efficient counterbalancingelement making full utilization of the space available and alsoproviding the advantage that the failure of one material will be atleast partially offset by the counterbalancing action of the re mainingmaterial.

As indicated above the elastomer may be used as a they may be appliedeither in a compressed or stretched position depending upon whether thepower unit is to provide its counterbalancing force in its closed orextended position. The unit illustrated in FIGS. 7 and 8 has a pair oftelescoping outer members 42 and 43. The end surfaces of the telescopingsupport members have fluid seals 44 at their edges. This permits theaddition of hydraulic forces to supplement the forces of the elastomerand springs.

FIGS. 9 and 10 illustrate a spring counterbalancing unit generallysimilar to that shown in FIGS. 7 and 8 except that the elastomer 45 ispositioned within the spring coils 46 so that the spring 46 and theelastomer 45 may be separately formed and assembled within the outertelescoping cylinders 47 and 48. This unit may be employed in the samemanner as FIGS. 7 and 8.

FIGS. 11 and 12 show tubular counterbalancing elements 50 which alsoreplace the springs such as are illustrated in FIGS. 5 and 5a and wherethe entire spring force is replaced by an elastomer. In this embodimentthe elastomer 51 is mounted in the individual telescoping cylindricalmembers 52 and 53 so that the elastomer may be stretched or corked by arelatively low capacity hydraulic system which supplies fluid within thetelescoping members 52 and 53 to extend the members and to stretch theelastomer preparatory to the application of the counterbalancing forceto the member. For example, the stretched elastomer might be used toprovide a counterbalance for a dump truck bed so that the elastomerelements may be tensioned by a low capacity hydraulic system during thetime that the dump truck is being loaded or is moving between pick-upand discharge points. Such a system permits the stretch or build-up of arelatively large lifting force from a low capacity hydraulic chargingunit.

FIGS. 13 and 14 illustrate the use of an elastomer 55 for providing acounterbalancing force in connection with a hydraulic drive cylinder 56.In this embodiment the elastomer 55 is mounted concentrically of thehydraulic drive cylinder 56 with the tubular elastomer having aplurality of laminations 57. In this way, the series of laminationsprovide for increased reliability as the laminations apply their forceindependently of each other to provide a more even force and to providean element of safety in the event of failure of one of the laminations.

FIG. 15 shows a hydraulic drive cylinder 60 including telescoping outercylindrical members 61 and 62 sealed to contain the hydraulic driveforces and including a central elastomer element 63 anchored at theopposite ends of the cylinder. This takes advantage of the extremelyhigh counterbalancing forces which it has been found may be obtainedwith such elastomers and provides an extremely compact and eflicientpower unit with an integral counterbalancing element.

The embodiment illustrated in FIG. 16 includes a steel spring 64 moldedwithin the elastomer element 65 to provide a composite counterbalanceproviding a certain amount of metallic support for the elastomer as wellas the combined forces of the steel and rubber which add an additionalelement of safety in the event of the failure of the one or the othercounterbalancing elements.

It will be seen that this invention provides important improvements inthe hydraulic drives for use with driven members requiringcounterbalancing forces. The power units of the invention provides thesecounterbalancing forces with integrally supported spring or elastomerelements or a combination of both and the various preferred mountingsfor these elements as described herein result in an extremely compactand reliable power unit which is useful in many applications whichpreviously required relatively cumbersome drive units and extremelyheavy counterweights.

In addition the power units described herein provide drive units adaptedfor handling heavy devices or members with considerable safety as theintegral construction 7 provides for counterbalance and driving and alsois adapted for the convenient adaptation of fail safe brake elements allwithin the compact package described.

The novel applications of small distributed springs and also the noveluse of elastomers alone or in combination with springs providesrelatively large counterbalancing forces in units only slightly largerthan those including only the hydraulic drive system itself. In this waynot only has an improved power unit been provided but the weight andsize of the entire structure may be reduced due to the elimination ofthe conventional counterweights or extremely heavy prior hydraulicdrives or electromechanical drive systems.

As various changes may be made in the form, construction and arrangementof the parts herein without departing from the spirit and scope of theinvention and without sacrificing any of its advantages, it is to beunderstood that all matter herein is to be interpreted as illustrativeand not in a limiting sense.

Having thus described my invention, I claim:

1. An hydraulic drive device comprising the combination of an hydraulicdrive motor having an hydraulic cylinder and cooperating piston and apiston rod, a first pair of telescoping cylinders mounted concentricallyand in spaced relationship to said hydraulic cylinder and forming anannular cavity with said hydraulic cylinder, one end of one of saidtelescoping cylinders being coupled to the piston rod, one end of theother of said telescoping cylinders being coupled to said hydrauliccylinder, a plurality of spring elements mounted in spaced relationshipin said cavity and operatively connecting said ends of said telescopingcylinders and each of said spring elements being enclosed in secondtelescoping cylinders, said second telescoping cylinders operativelyconnecting said ends of said first pair of telescoping cylinders, andsaid second telescoping cylinders being hydraulically sealed and adaptedfor being coupled to a source of hydraulic fluid.

2. The hydraulic drive device as claimed in claim 1 in which said springelements comprise elastomer and steel.

3. The hydraulic drive device as claimed in claim 1 in which said springelements comprise steel coil springs.

4. The hydraulic drive device as claimed in claim 1 in which said springelements comprise elastomer with steel spring embedded therein.

5. The hydraulic drive device as claimed in claim 1 in which said springelements comprise an elastomer inner element surrounded by a steel coilspring.

References Cited UNITED STATES PATENTS 2,408,915 10/1946 Cones 92132 X2,461,780 2/1949 Smith 92130 X 2,497,489 2/1950 Coursen et al. 92-130 X2,535,600 12/1950 Rappl 2--132 X 2,605,099 7/1952 Brown 267-33 2,851,0119/1958 Chasser 92-132 X 2,896,583 7/1959 Stixrood 92132 X 3,208,7679/1965 Moulton 267-33 X 3,298,664 1/1967 Dixon 92130 X 3,308,496 3/1967Mooney et al. 14-36 FOREIGN PATENTS 487,735 11/ 1952 Canada.

r 926,475 4/ 1947 France.

326,477 3/1930 Great Britain.

OTHER REFERENCES Engineering News-Record, Hydraulics Operate BasculeSpan, May 2, 1963, page 33.

MARTIN P SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner.

